It is known in the art that both softwood and hardwood can be compressed into densified and hardened products. There are many ways of achieving this including the use of heat, steam, pressure and chemicals including adhesives. The objective of a process of wood deformation is to achieve both densification of the wood and permanent fixation of the densification in the product in a manner which is efficient and has minimal effect on the environment.
A discussion of possible ways in which to achieve permanent fixation of compression deformation of soft wood is found in Inoue (see reference). The author of that paper suggested that three methods to permanently fix the compression deformation of wood. The first was to make wood inaccessible to water using acetyl groups. The second was to form cross-linking between wood components using para-formaldehyde. The third was to release elastic energy stored by deformation by dipping compressed wood in acidic acid and hydrochloric acid.
In U.S. Pat. No. 3,981,338 there is described a method of compressing debarked and dried logs in a mould where they were immersed with a liquid adhesive. The logs were compressed in the mould to a thickness smaller than that finally required. They were then allowed to expand while still immersed in the adhesive and compressed to the final desired thickness and subjected to an elevated temperature to allow the adhesive to harden.
In U.S. Pat. No. 4,606,388 there is described a method of compressing low density woods. A wood member in a green state is subjected to ammonia to plasticise it to a sponge-like form. It is then subjected to a series of compression cycles and dried.
In published Japanese application Nos. JP 10-217210; JP 11-114915; and JP 11-320510 there are described methods of forming pressed wood using high pressure compressing devices.
In U.S. Pat. No. 5,343,913 there is described a method of compressing wood involving softening the wood at high temperature and high water vapour temperature and then compression moulding the wood to reduce it to one half to one third of its original thickness. The compression is fixed by maintaining wood in a compressed stated for a predetermined period of time.
It is an object of this invention to provide a method of manufacturing densified wood with permanent fixation which is an alternative to the above described methods or at least to offer the public a useful choice.